HELP WITH HEAT RECOVERY SYSTEM

moby30

Just looking for some information on Heat recovery systems as the one I installed a few years back seems to do nothing but blow cold air into rooms making them colder then the heating kicks in which is the opposite of what I thought should happen. I installed it myself and checked then double checked and even had the people I bought it off say it was 100%. The other problem is that the extraction point in one of the bathroom which would also be nearest the actual unit leaks a lot of water every few months? Any help would be greatly appreciated as I cannot get any answers from the people I bought it off and very few people seem to know anything about them.

The Parrot

first things to check are one what is the efficiency meant to be of the unit , and do you have the pipes in the roof. and if so do you have them in properly insulated.

but dont forget no matter what the heat recover will never recover all your heat it will put slightly colder air back into the room than it takes out. as its designed so you can have ventilation with out loosing all the heat only some of it.

heavydawson

moby30 wrote: »

Just looking for some information on Heat recovery systems as the one I installed a few years back seems to do nothing but blow cold air into rooms making them colder then the heating kicks in which is the opposite of what I thought should happen. I installed it myself and checked then double checked and even had the people I bought it off say it was 100%. The other problem is that the extraction point in one of the bathroom which would also be nearest the actual unit leaks a lot of water every few months? Any help would be greatly appreciated as I cannot get any answers from the people I bought it off and very few people seem to know anything about them.

Moby, I think it's fair to say you should not have cold air blowing into a room from your MHRV unless the rooms the extract is coming from are colder than the rooms the "warm" air is being sent to. I guess this is possible if you have a few un-used or un-heated bathrooms. Would you say your extract rooms are colder than your "insertion" rooms?

moby30

Thanks for the replies. The pipe work is running behind the walls of the upstairs rooms and is completely sealed and covered in some places as much as 12" of insulation. I have 3 extract rooms, the Utility and two Bathrooms as per the recommendations and its fair to say that the Bathrooms would be no colder than any of the other rooms and the ports are closed unless we are using the showers etc. The Utility is almost always very warm and humid depending on whats running but still the air being fed into the rooms is almost like air conditioning. I was wondering if its because both bathrooms are almost directly under the unit where as the utility is the furthest away

MicktheMan

moby30 wrote: »

and the ports are closed unless we are using the showers etc.

What do you mean by this?

The Parrot

well if i understand this correctly, the bathroom ports are being closed would mean that the only air supply its getting at most times is from one room, from a lamens point of view, there just cant be enough heat to heat the amount of air coming into the house. so by the time your utility room gets to the unit its alittle colder and with the outside temps at the moment it would have to have 99% efficients to get the heat into it i would assume

ShiverinEskimo

Many HRV units come with a summer bypass feature that skips the heat exchanger for when you don't need heat recovery in the summer.

Could be something as simple as that feature being left on for the winter and so just pumping in un-heated outside air.

moby30

MicktheMan wrote: »

What do you mean by this?

The three rooms we use for extracting the warm air were the two Bathrooms and the Utility. We were told to keep the Bathroom ports closed as they tend to be the coldest rooms in the house but to open and put the unit onto full power when having showers etc. The Utility is always warm so we just leave it open.
The unit does have a frost protection function and a summer by pass which are operated automatically but because the air coming into the rooms is so cold Im starting to think that this is the problem.
Im also wondering about if its such a good idea to have the bathrooms as extraction points I always thought having some sort of extract behind the Fridge might work as youd be getting constant warm air
Thanks again for all the replies

ShiverinEskimo

moby30 wrote: »

Im also wondering about if its such a good idea to have the bathrooms as extraction points

It most definately is. This is crucial to help avoid problems caused by condensation.

I've just had my HRV first fix done and we put extracts near the cooker and in all bathrooms specifically over the showers/baths. This is to get the moist air out of the room and back to the HRV asap before it can condense on the walls/windows and encourage mould growth.

My HRV unit has a condenser and drainpipe to allow this moisture to be disposed of. Depending on your model something similar might be in place.

creedp

moby30 wrote: »

The three rooms we use for extracting the warm air were the two Bathrooms and the Utility. We were told to keep the Bathroom ports closed as they tend to be the coldest rooms in the house but to open and put the unit onto full power when having showers etc. The Utility is always warm so we just leave it open.
The unit does have a frost protection function and a summer by pass which are operated automatically but because the air coming into the rooms is so cold Im starting to think that this is the problem.
Im also wondering about if its such a good idea to have the bathrooms as extraction points I always thought having some sort of extract behind the Fridge might work as youd be getting constant warm air
Thanks again for all the replies

I dont understand how your unit is properly balanced if you close 2 of the extracts most of the time. It is difficult to see how one extract can extract the same amount of air as what is being supplied into all the other rooms in the house. If it is balanced with that set up, then you are at risk of creating negative pressure within the house when you open the 2 bathroom extracts especially if you only do this at the full speed setting. I have never heard of this set up myself and would be concerned with it especially if you have a stove.

Also I don't understand why you bathrooms are so cold .. do you not heat them? If these rooms are colder than the adjacent rooms they are simply robbing heat from the warmer rooms .. you would be better off in my uneducated opinion to keep the bathrooms at same temp as rest of house and leave the extracts open. By the way how do you extract the 'bathroom smells' in an airtight house without extracts in the bathrooms? Do you open windows .. is this why your bathrooms are cold?

Also if you have no extract in the kitchen are you not in danger of creating condensation problem with steam from cooking etc. Maybe you have an externally ducted cooker hood to do this job. If so you are wasting a lot of warm air that could be extracted by the HRV unit and used to heat the incoming air. Also the kitchen extract would extract the hot air from the fridge, oven, dishwasher, etc

ShiverinEskimo

creedp wrote: »

I dont understand how your unit is properly balanced if you close 2 of the extracts most of the time. It is difficult to see how one extract can extract the same amount of air as what is being supplied into all the other rooms in the house.

The same air is not re-circulated. It is pumped out minus the heat which is transferred to the incoming air. You are right that they should open the extracts - fewer extracts means less heat to transfer which means more colder air coming in.

creedp wrote: »

By the way how do you extract the 'bathroom smells' in an airtight house without extracts in the bathrooms? Do you open windows .. is this why your bathrooms are cold?

As the air is not re-circulated 'bathroom smells' are pumped out with the rest of the stale air.

creedp

ShiverinEskimo wrote: »

The same air is not re-circulated. It is pumped out minus the heat which is transferred to the incoming air. You are right that they should open the extracts - fewer extracts means less heat to transfer which means more colder air coming in.

I agree air is not being recirculated - its the second issue above is the issue I am referring to.

As the air is not re-circulated 'bathroom smells' are pumped out with the rest of the stale air.

Where is the stale air extracted from though? It can't be extracted from the bathrooms as the extract is closed or are the extract points opened each time the bathroom is used? If no extracts in the bathrooms the stale air in the bathrooms will be drawn towards the utility room as this is the only extract point open, and therefore through the living area of the house. That is not an ideal situation I would have thought. There is a reason bathrooms need extracts points whether it be vents in windows/walls/forced extraction through electric vents. When these vents are replaced by a MHRV then the vents need to be open permanently or else the stale air cant be extracted. Maybe Im reading all this wrong!

ShiverinEskimo

creedp wrote: »

When these vents are replaced by a MHRV then the vents need to be open permanently or else the stale air cant be extracted. Maybe Im reading all this wrong!

No I think you're on the money. I don't know why one would close the extract vents. System is designed to have a balance between warm extract and cold intakes so that the heat exchanger can be effective at pre-heating the incoming air and so that stale air is replaced. Need to remember MHRV should be ventilation first, heat recovery second - a house needs to be ventilated.

moby30

This is part of my reason for asking for help. What yous both say is common sense to me and my thinking has always been that the Unit itself is faulty and that the company that supplied it is just making all sorts of lame excuses. My understanding before I even bought the unit was that Its just a straight forward enough unit that you leave running in the background and aswell as heat fresh air coming in it extracts stale air and odours while also eliminating condensation etc. But the air coming through is as cold as the air outside and always has been plus water is building up in one of the bathroom extracts. As I said the company recommended closing ports which has never made sense to me and I ve only been doing since January but have now stopped esp since seeing the replies here so thanks for that. I reacon at this stage its a faulty Bypass which is supposed to kick in and act like an air cooler in very warm weather. Thanks again for the very helpful replies
BTW should there be an equal amount of Intakes Vs Outtakes. I have 7 Intakes and 5 Extracts(I mistakenly said 3 in an earlier post)

MicktheMan

moby30 wrote: »

This is part of my reason for asking for help. What yous both say is common sense to me and my thinking has always been that the Unit itself is faulty and that the company that supplied it is just making all sorts of lame excuses. My understanding before I even bought the unit was that Its just a straight forward enough unit that you leave running in the background and aswell as heat fresh air coming in it extracts stale air and odours while also eliminating condensation etc. But the air coming through is as cold as the air outside and always has been plus water is building up in one of the bathroom extracts. As I said the company recommended closing ports which has never made sense to me and I ve only been doing since January but have now stopped esp since seeing the replies here so thanks for that. I reacon at this stage its a faulty Bypass which is supposed to kick in and act like an air cooler in very warm weather. Thanks again for the very helpful replies
BTW should there be an equal amount of Intakes Vs Outtakes. I have 7 Intakes and 5 Extracts(I mistakenly said 3 in an earlier post)

One definitive way to know if the "heat recovery" is happening is to observe the condensate drain from the unit. If there is a regular drip then there is some heat recovery happening. If the bypass is faulty or excessive ducting heatloss and no heat recovery happening then there wont be any condensate forming in the unit and the drain will be dry.
Another reason for cold air being supplied is that the supply and extract ducting layout is poorly designed and/or inadequately insulated. If there is excessive heatloss over the length of the ducting then the air coming in will be a lot cooler than it should be. Is the supply/extract ducting installed inside or outside the thermal envelope?
What do you mean by water buildup in the bathroom extract? Is it buildup happening in the ducting? If it is then this may indicate an issue with the ducting insulation.
The system needs to be balanced, in that, the volume of air being extracted should be the same as the volume being supplied. By closing of some of the bathroom extract grills will interfere with this balancing.
Who commissioned the system? Was it balanced then and how was it done?

CJhaughey

Are the ducts connected correctly?
Many HRV units are setup incorrectly by incompetant installers.

1100010110

OP, What kind of ducting is in the attic space? Is it rigid with flexible only at the HR unit or is it all flexible?

moby30

The ducting is all rigid plastic except for the fresh air into the HRV and extracted air from the HRV which is flexible.

josip

My tuppence worth to OP and other posters.

• Measure the room temp, temp of the air coming into the room 10cm into the duct (measure at least 3 ducts for consistency) and outside air temp. Airflow can appear colder than it actually is due to wind chill.
• The system should be statically balanced and not need some ducts to be opened/closed periodically.
• The number of extracts do not have to equal the number of inputs, the system just has to be balanced.
• As tempting as it might seem, don't run the hob extractor into the HRV. The grease will clog up the filters and heat exchanger. Best case will be a system that doesn't work. Worst case will be costly repairs.
• Condensation dripping from internal ducting would imply that pipe is cold. If the bathroom extract isn't permanently open and that pipe isn't adequately insulated it's reasonable that when it is opened, al the moisture will condense.

Flynner30

Hi,
I am building a 2 storey house and ready to install heat recovery, am enquiring does anyone have any information on systems, and which would be best to go with including company?
Is anyone familiar with -snip- heat recovery system BV 400?